Biochemistry of a special relationship: Coral reefs would not exist if there was not a special chemistry between the coral polyp and the green algae that live inside it

A CORAL REEF is the biggest and most spectacular structure made by living things. Yet although it looks permanent and indestructible, it is neither. On a geological timescale, reefs are at the mercy of global climatic changes: continual changes in sea level, in the patterns of circulation on the sea's surface and in temperature. On shorter timescales, reef-building corals have been devastated repeatedly by regional events, both environmental - cyclones for instance - and biological, such as attack by crown-of-thorns starfish. In the shortest timescale, human activity can be just as damaging: small increases in the amounts of nutrients in the water are potentially lethal to most reef-building corals.

The organisms primarily responsible for building modern reefs are hermatypic corals (from the Greek, herma=reef) and the microscopic photosynthetic algae that live symbiotically in their tissues. These algae, dinoflagellates commonly called zooxanthellae, are essential to the existence of coral reefs. But ...

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